1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same. The present invention particularly relates to a semiconductor device having a semiconductor chip whose back is exposed, and a method for manufacturing the same.
This application is the counterpart of Japanese patent application, Serial Number 250483/2001, filed Aug. 21, 2001, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
With size reductions in portable devices, there has been a demand for a reduction in the size of semiconductor devices in the portable devices. In order to meet such a demand, a semiconductor device called a xe2x80x9cChip Size Packagexe2x80x9d having outside dimensions approximately identical to those of a semiconductor chip has come along. As one form of the chip size package, there is known a semiconductor device called a xe2x80x9cWafer Level Chip Size Packagexe2x80x9d or xe2x80x9cWafer Level Chip Scale Packagexe2x80x9d. In such a wafer level chip size package (hereinafter called xe2x80x9cWCSPxe2x80x9d), the surface of a semiconductor chip (semiconductor substrate) is sealed with a resin, whereas the back (silicon surface) thereof has an exposed structure.
Such a WCSP is mounted on a printed circuit board so that the surface side of the semiconductor chip is placed face to face with the printed circuit board. Namely, the WCSP is placed on the printed circuit board in a state in which the back of the semiconductor chip is being turned up.
Thereafter, a visual inspection is effected on the WCSP placed on the printed circuit board. As items intended for the visual inspection, there may be mentioned, for example, a position inspection and a height inspection. The position inspection is carried out to check whether the WCSP is placed in a predetermined position on the printed circuit board. The height inspection is made to check whether the WCSP is placed aslant to the surface of the printed circuit board.
A device using a laser beam is known as a visual inspecting device for executing the above-described visual inspection. This type of visual inspecting device carries out the following operations.
A laser beam emitted from a laser light source mounted to the visual inspecting device is first applied to the printed circuit board and an electronic part (WCSP) to be inspected. The irradiated laser beam is reflected by the printed circuit board and the electronic part (WCSP), and a light detecting or receiving device attached to the visual inspecting device receives such a reflected laser beam. The printed circuit board is shifted in an X-axis direction or a Y-axis direction to thereby carry out a series of operations for the application and reception of the laser beam. Namely, the laser beam scans over the electronic part (WCSP) and the printed circuit board. The visual inspecting device measures the difference between the intensity of the laser beam applied from the laser light source and the intensity of the laser beam received by the light receiving device during the series of operations. Thus, the visual inspecting device recognizes the outer shape (contour) of the electronic part (WCSP). The visual inspecting device executes the position and height inspections, based on the result of recognition.
In the WCSP, however, the back (silicon surface) of the semiconductor chip is ground to further thin the thickness of the WCSP and due to reasons such as the difference between the linear expansion coefficient of silicon and that of the printed circuit board. Therefore, the silicon surface thereof is held in a mirror state. When the laser beam is applied to the WCSP having such a silicon surface held in the mirror state and the printed circuit board as described above, the difference between the intensity of light reflected by the printed circuit board and returned to the light receiving device and the intensity of light reflected by the WCSP and returned to the light receiving device is small, i.e., the contrast is low. Therefore, the visual inspecting device had difficulty in recognizing the outer shape (contour) of the WCSP. Accordingly, the visual inspecting device has encountered difficulties in determining whether the WCSP is placed in the predetermined position on the printed circuit board or mounted aslant to the surface of the printed circuit board.
Thus there has been a demand for a semiconductor device that makes it easy to perform a visual or optical inspection.
It is an object of the present invention is to provide a semiconductor device having improved structure for performing an easy visual inspection.
According to one aspect of the present invention, there is provided a semiconductor device that includes a semiconductor substrate which has a first main surface having circuit elements formed thereon, a second main surface substantially opposite to the first main surface, and a plurality of side faces provided between the first main surface and the second main surface. The semiconductor device also includes a plurality of external terminals formed over the first main surface and respectively electrically connected to the circuit elements. The second main surface has a central area and a peripheral area surrounding the central area, and a first steplike section formed in the peripheral area.
The above and further objects and novel features of the invention will more fully appear from the following detailed description appended claims and the accompanying drawings.